This document contains final regulations governing the extent to which taxpayers may elect the Federal income tax benefits provided by section 1400Z-2 of the Internal Revenue Code (Code) with respect to certain equity interests in a qualified opportunity fund (QOF). The final regulations address the comments received in response to the two notices of proposed rulemaking issued under section 1400Z-2 and provide additional guidance for taxpayers eligible to elect to temporarily defer the inclusion in gross income of certain gains if corresponding amounts are invested in certain equity interests in QOFs, as well as guidance on the ability of such taxpayers to exclude from gross income additional gain recognized after holding those equity interests for at least 10 years. The final regulations also address various requirements that must be met for an entity to qualify as a QOF, including requirements that must be met for an entity to qualify as a qualified opportunity zone business. The final regulations affect entities that self-certify as QOFs and eligible taxpayers that make investments, whether qualifying or non-qualifying, in such entities.